With the rapid increase of complexity of computing, communication, and other systems, increasing amounts of power are needed to maintain operations in many systems. The increased system complexity often results in longer handling operations in the case of system power loss. For example, in a system power loss event, these systems require longer power hold-up time to properly save operation parameters of the components and/or to engage back up power supplies. The power hold-up time is the amount of time that the system can continue to run without resetting or rebooting during a power interruption.
Higher system power and longer hold-up time requirements put increasing pressures on power supply design. These designs typically require larger energy storage devices, which translates into higher costs and larger equipment sizes. To resolve this technical challenge, conventional systems have attempted to detect the input power loss at the earliest possible time to allow power loss reaction processes to begin as early as possible.
Alternating current (“AC”) voltage changes instantaneous amplitude continuously from zero to its positive and negative maximum values in sinusoidal cycles. Conventional systems passively detect AC input voltage over a time window and, based on the voltage values, determine whether the AC power is still present or has been lost. When the voltage across the load drops below a certain level, an AC loss condition is detected. One disadvantage of this method is that the AC power loss may not be detected until one or more AC cycles later.
Other conventional methods read an instantaneous AC voltage and compare the read value against a sampled and delayed version of the data. Still other conventional methods read instantaneous AC voltage and compare the instantaneous values over a short period of time T, such as T=1 mS or T=0.5 mS, against standard AC waveform values to determine whether the AC input voltage remains within the range of a standard sine wave, or has dropped out of the range indicating a loss of AC power. This conventional solution creates a conflict between seeking a fast response to AC power loss when a shorter T is used, and avoiding a false positive response when the system mistakenly considers an AC line glitch as an AC power loss.